Filter



mm m T F I 2 @WAW R F. NORRIS July 5, 1938.

FILTER Filed Nov. 9, 1934 Patented July s, 1938 Ralph Forbush Norris,Madison, Wis, assignor to O. F. Burgess Laboratories, Inc., Chicago,111., a corporation of Delaware Application November 9, 1934, Serial No.752,246

8 Claims. (Cl. 183-45) This invention relates to improvements in filtersand in particular filters used for cleaning the intake air of internalcombustion engines.

Among the objects of this invention are the providing of a. highlyefficient cleaner which has a high capacity, has a low air restriction,oc-

' cupies a relatively small space and is relatively cheap to construct.

The following specification should be read in connection with theaccompanying drawing in which: I

Fig. 1 is a detailed view showing the construction of the gimpedmaterial of which the filter is made;-

Fig. 2 is a sectional view of an annular cylinder filter unitincorporating the gimped material of Fi Fig. 3 is a side elevation of across-wound cylindrical filter in which the carrier strands only areshown for-clarity; and

Fig. 4 is a view similar to Fig. 1 showing a construction in which aplurality of gimped members are arranged upon a single carrier strand.

Air filters satisfactory for internal combustion l engines andespecially automobile engines should have the characteristics listedabove. The filter of my invention. has these characteristics.

The gimped material ID of Fig. 1 is the basis of my improved filterbody. It is made of a central flexible carrier strand l2 about which asecond strand i4 is wound or gimped in the form of a helix. The strandI4 is made of a springlike material so that the helix is substantially ahelical spring along the length of carrier strand II. The use of thisspringlike and resilient helix for the gimped material is a novelfeature of my invention. Strand if is preferably made of metallicribbon. Mechanically worked copper ribbon is usually used althoughaluminum, iron and any other metal or alloy may be used which has thedesired physical properties or which may be either heat-treated orphysically worked to give it the desired resiliency or springiness.Copper is the metal which is favored at present for automobile enginefilters.

Excellent results are obtained with a filter body made as hereinafterdescribed from a gimpedmaterial made or spring-like copper ribbonstrands 0.025 inch wide b 0.002! inch thick, the helical spring being0.1 5 inch in diameter with 18 coils per inch of length. Thesedimensions are merely illustrative, and my invention is not limited togimped material made from copper ribbon of these dimensions.

Although the carrier strand i2 is indicated as being made of metalribbon, nevertheless it may be made of any suitable flexible materialwhich may be ordinary wire, yarn, textile cord, or any textile fabricwhich is not too large in proportion to the helix.

The shape of the filter body is determined annular cylinder as shown inFig. 2 is used to a large extent for automobile intakes.

It is apparent that the type of winding also affects the characteristicsof the finished cleaner. For example, winding under considerable tensionresults in a compact cleaner having small openings and a highrestriction. The gimped material may be spool-wound, which is the typeof winding used on ordinary spools ,of thread. It may also becross-wound as shown in Fig. 3, this type of winding being preferred.

The preferred cross-wound filter body of Fig. 3 shows a structure inwhich the strands of gimped material in any one layer are spaced apart.The adjacent coils in any layer preferably are spaced apart at leastabout the diameter of the coils except at the edges where overlappingoccurs. This spacing of the strands when combined with a light tensionproduces a filter body that is highly eiiicient with the above describedgimped material. The cross winding should be effected in such a mannerthat a honeycomb structure is not produced, that is, the strands inalternate layers should be staggered as indicated by strand ii in Fig. 3and should not be in alignment. As shown the layers are wound about asingle'axis of the frame. The direction of the air flowing through thefilter thereby is changed frequently. A more homogeneous filter bodyalso is produced thereby. The annular cylindrical filter body of Fig. 2may be produced by cross winding in the absence of retaining side walls.Such side walls are necessary if spool winding is used in order to keepthe strands from rolling outwardly. Furthermore, cross winding preventsbunching of the gimped material which is characteristic of spool windingand thereby produces a filter of uniform porosity. It is essential totype are dipped in oil and drained before being put into service, theretained oil catching the dust passing through the coils. Each loop ofthe coils of wire is an eflicient retainer of 011 since the oil gathersas a droplet at the bottom thereof. These coils therefore retain a largeamount of oil which in turn catches a large amount of dust. Because ofthe large number of loops and the large volume of voids the filter iscapable of retaining a large quantity of dust before becoming cloggedand it therefore has a high capacity.

Since the flexible carrier strand is relatively straight its oilretaining capacity is small if it is made of a single strand of metal.It therefore does not contribute greatly to the dust retaining capacityof the filter. Twine or cord or similar absorptive material functionsmechanically in a manner similar to metallic wire or ribbon when used asthe carrier strand. However, it retains a relatively large amount ofoil] because of its wick-like properties and thereby adds to thecleaning efiiciency and dust capacity of the filter. I

When the filter is made in the form of an annular cylinder the gimpedmaterial I8 is cross wound exteriorly on a cylindrical screen or cloth20. A second cylindrical screen or cloth 22 is mounted exteriorly of thecross wound gimped material where it may be soldered in place. Theexposed strands of gimped material at the ends of the cylinder catchreadily on any projecting points and therefore it is desirable to tiethem in place to facilitate handling during assembly operations andduring service. This is done by laying, before winding, four or morestrands of gimped material 24 on the face of the inner cylinder 20,parallel to the axis thereof. These strands, being longer than thecylinder, project beyond the end and are held in this position on theface of the inner cylinder when the filter is formed upon them. Afterthe winding is completed the projecting ends of these tie strands areturned over the ends of the annular cylinder of gimped material l8 asshown at 26 and held between the outer cylinder 22 and gimped materiali8 when the outer cylinder is slipped into place.

In Fig. 4 of the drawing the gimped material 30 comprises a centralflexib-ie carrier strand 32, having a plurality of strands 34 wound orgimped thereon in the form of a helix. The form shown in Fig. 4 consistsof a pair of gimped strands arranged upon a single carrier strand, butwill be apparent that any number of strands may be gimped on the carrierstrand. The gimped material of Fig. 4 possesses the characteristicsheretofore described in connection with Figs. 1 to 3 and it may be usedin the construction of a filter body by winding it into the desired formas heretofore described in connection with Figs. 2 and 3, of thedrawing.

The above specific example of my invention illustrates the principlesinvolved therein. It will be apparent to those skilled in the art thatconstructions may be used which vary in detail over a considerable rangeand that equivalent constructions may be used without departing from thescope of the fc-ilowing claims. Two or more strands of the gimpedmaterial l0 may be wound'simultaneously to form thefilter instead of thesingle strand as described.

I claim:

1. A filter body comprising an interstitial structure of a plurality ofoverlying layers of strands of gimped material comprising a flexiblecarrier strand having one or more metallic spring-like ribbons gimpedthereon in the form of a continuous helical spring wound about saidcarrier strand throughout the length thereof. said strands of gimpedmaterial being wound upon a foraminous cylinder, the strands or" gimpedmaterial being cross wound, and the strands in any one layer beingspaced apart.

2. A filter body in the form of an annular ring comprising overlyinglayers of cross-wound strands of gimped material comprising a flexiblecarrier strand and one or more metallic springlike strands gimpedthereon in the form of a continuous helical spring wound about saidcarrier strand throughout the length thereof, said spring-like strandshaving sufficient stiffness to retain their shape when in operation in afilter of the type herein described.

3. The filter body of claim 2 in which the carrier strand is under lighttension and in which the spring-like strands are in the form of ribbon.

4. The filter body of claim 2 in which the strands of gimped material inany layer are spaced apart on the average a distance equal to at leastthe diameter of said helicai spring.

5. The filter body of claim 2 in which the strands of gimped material inany layer are spaced apart, and the strands in alternate layers arestaggered to change the direction of the air flowing through the openingbetween said spaced apart strands.

6. A filter body comprising an interstitial structure of a plurality ofoverlying layers of one or more strands of gimped material comprising aflexible carrier strand having one or more metallic spring-like strandsgimped thereon in the form of a continuous helical spring Wound aboutsaid carrier strand along the length thereof, the strands of gimpedmaterial in one layer extending crosswise cf the strands in the adjacentlayer and the strands in any one layer being spaced apart.

'7. A filter body comprising an interstitial structure of a plurality ofoverlyin= layers of one or more strands of gimpefmaterial comprising aflexible carrier strand having one or more metallic spring=1ikc strandsgimped thereon in the form of a continuous helical spring wound aboutsaid carrier strand along the length thereof, the strands of gimpedmaterial in one layer extending crosswise of the strands in theadjacentlayer.

8. The filter body of claim 2 in the shape of an annular ring mountedbetween two telescoped foraminous cylinders, the gimped material beingwound upon the exterior surface of the inner cylinder.

RALPH FORBUSH NORRIS.

